1. Field of the Invention
This invention relates to the field of antivibration isolations for machines, in particular to elastic mountings for automobile motors or mountings for truck cabs. It relates to high-flexibility mountings with integrated hydraulic damping, increasing the apparent rigidity in a very limited range of rather low frequencies, by means of a column of liquid which is very long in relation to its cross section, the resonance of which counteracts large amplitude displacements, but without destroying an elastic filtering at higher frequencies.
A family of such elastic mountings is generally realized by means of a thick conical elastomer membrane which, when bonded to a support casing and to a central framework to fasten it to the housing to be suspended, e.g., a power unit, encloses a chamber containing a damping liquid forced into an expansion space, under low pressure, through a device with a long inertial column, the greatest part of the vertical load being borne by deformation of the elastomer constituting the conical membrane.
2. Description of the Prior Art
French Patent FR Nos. 2,467,724 and 2,511,105 (Peugeot) describe two devices of the type described above and which have the advantage of integrating into the elastic device the damping column housed in a rigid wall immersed in the hydraulic circuit thus constituted, after sealing, e.g., by crimping on an attachment cover for the casing, of the mounting, which is thereby made into a one-piece component.
When such an apparatus, which exhibits great flexibility in all directions, is used for the suspension of a power unit, it absorbs the reactions due to the motor torque, producing large longitudinal deformations, which are prejudicial to fatigue strength, which are remedied by the installation of limit stops, such as those described in the French continuation FR No. 2,543,494 to Pat. No. 2,535,261 (Citroen and Peugeot).
The above-mentioned patents are incorporated herein by reference as if the entire contents thereof were fully set forth herein.
An analysis of the prior art shows that there is a contradiction between the desire for great flexibility, which is advantageous for good filtering of vibrations, and the desire for long term strength in the presence of the large forces resulting from installation on a power unit, which exerts the motor torque geared down by the shortest transmission ratios on the short lever constituted by its elastic mountings.